ELECTROCHEMICAL REDUCTION OF CO2 AT CU+AU ELECTRODES

The electrochemical reduction of CO2 and HCHO was studied at copper and Cu + Au electrodes. The experiments were performed at 25-degrees-C in 0.1 M KCl solution saturated with CO2, under atmospheric pressure. The reduction of CO2 at Cu + Au electrodes leads to a decrease in the mean current efficiency (CE) for methane, formic acid and alcohols and to an increase in CE for CO and H2, as coverage of the copper surface by gold is increased. The CE for ethylene formation displays a small maximum for low coverage of the copper surface with gold, and consequently a decrease with increasing surface coverage. CE values for all the electrolysis products are more stable over time at Cu + Au electrodes than at copper electrodes. Electroreduction of formaldehyde at copper and Cu + Au electrodes indicated characteristics qualitatively similar to those of carbon dioxide, as regards the shape of the CE vs. time curves for methane formation. Small amounts of unknown organic compounds were detected in solution during the electrolysis of both CO2 and HCHO at Cu + Au electrodes.